This invention relates to a modular printhead. More particularly, the invention relates to the assembly of such a modular printhead. Specifically, this invention relates to a mounting of a printhead in a support member of a modular printhead.
The applicant has previously proposed the use of a pagewidth printhead to provide photographic quality printing. However, manufacturing such a pagewidth printhead having the required dimensions is problematic in the sense that, if any nozzle of the printhead is defective, the entire printhead needs to be scrapped and replaced.
Accordingly, the applicant has proposed the use of a pagewidth printhead made up of a plurality of small, replaceable printhead modules which are arranged in end-to-end relationship. The advantage of this arrangement is the ability to remove and replace any defective module in a pagewidth printhead without having to scrap the entire printhead.
It is also necessary to accommodate thermal expansion of the individual modules in the assembly constituting the pagewidth printhead to ensure that adjacent modules maintain their required alignment with each other.
According to the invention, there is provided a printhead which includes
a receiving member defining a receiving zone;
at least one printhead module received in the receiving zone of the receiving member; and
complementary locating formations carried by the receiving member and said at least one printhead module, the locating formations enabling relative movement of the printhead module, due to expansion, in three orthogonal axes relative to the receiving member.
Preferably, the receiving member is a channel shaped member having opposed walls interconnected by a bridging portion to define a channel which forms the receiving zone. Accordingly, the three orthogonal axes may be an x axis, being an axis parallel to a longitudinal axis of the channel shaped member, a y axis being in the same plane as the x axis but at right angles thereto and a z axis which is at right angles to the plane.
For a pagewidth printhead, the printhead may include a plurality of printhead modules arranged in end-to-end relationship in the channel, each printhead module carrying a printhead chip and adjacent modules abutting each other such that the printhead chips of adjacent modules overlap.
Thus, each module may be elongated, may be stepped at its end and the printhead chip may be arranged at an angle to a longitudinal axis of the module. The longitudinal axis of the module may extend in the x-direction.
Each printhead module may have a set of locating formations and the channel of the channel shaped member may have a complementary set of locating formations at each module location in the channel.
The locating formations of the channel shaped member at each module location may include a pair of longitudinally spaced engaging formations arranged on one wall of the channel and a securing means arranged on an opposed wall of the channel; and the locating formations of each module may include a pair of longitudinally spaced co-operating elements arranged along one side of each module for co-operating with the engaging formations and a complementary element on an opposed side of the module for co-operating with the securing means.
One combination of engaging formation and co-operating element may serve to locate the module relative to the channel in a longitudinal, or x direction, the other combination of engaging formation and co-operating element allowing longitudinal, expansionary displacement of the module relative to the channel in the direction of the x axis.
The combinations of engaging formations and co-operating members, due to shapes of said engaging formations and co-operating members may allow expansionary displacement of the module relative to the channel in a direction normal to a plane in which the module lies, i.e. in the direction of the z axis.
A combination of the securing means and the complementary element may allow expansionary displacement of the module relative to the channel in a direction of a plane in which the module lies but normal to a longitudinal axis of the channel, i.e. in the direction of the y axis.
To facilitate any expansion in the direction of the y axis, a width of the module may be less than a spacing between the walls of the channel.
The securing means may be a snap release carried on a resiliently flexible arm, the resiliently flexible arm forming part of said opposed wall of the channel.
The complementary element may be a stepped recess defined in the module approximately midway along its length for receiving the snap release.
Each engaging formation may be in the form of a hemispherical projection which projects inwardly from said one wall of the channel. A first co-operating element may comprise a conical recess defined proximate a first end of the module and a second co-operating element may comprise a slot, having a longitudinal axis extending parallel to the longitudinal axis of the channel, proximate a second end of the module, each of the conical recess and slot receiving one of the hemispherical projections therein. The slot may have a triangular cross-section when viewed in a plane normal to the longitudinal axis of the slot.